Set the initial value of maxfilesize to OFF_MAX in the
new NFS client. It will then be reduced to whatever the
server says it can support. There might be an argument
that this could be one block larger, but since NFS is
a byte granular system, I chose not to do that.

Suggested by: Matt Dillon
Tested by: Daniel Braniss (earlier version)
MFC after: 2 weeks